Michelin achieves greater energy efficiency in Dundee

Following the installation of a new cooling tower for process water, Michelin has managed to slash some 1,500 MWh from its Dundee plant’s annual energy consumption. The key to the savings is the new installation’s AC drives, which were supplied by Emerson Industrial Automation company Control Techniques. These AC drives control the speed of fans and pumps and match supply with demand; Emerson comments that when the cooling plant is idling, its energy consumption is now the equivalent to that needed to boil your cup of tea.

Speaking about the project, Control Techniques project manager Mike Barklie commented: “I measured actual cooling requirements and realised that there were further potential savings to be made by putting in variable-speed drives to match the supply of cooling water to demand. It was a major investment, but we have achieved a tremendously successful result that has a return on investment of less than three years.”

Control Techniques drives are already in service in other areas throughout the Dundee plant and other Michelin facilities around the world. Emerson comments that “several hundred” such drives are already installed on production lines, stirrers, extruders, pumps and fans throughout the 24,000 tyre per day Dundee factory. The new SPX Marley high-efficiency cooling tower has two 30 kW cooling fans for the dual 300m3 cells and there are six large pumps – three 22 kW pumps for the hot water to the tower and three 90 kW, 4.4 bar pumps to return the chilled water back to the factory.  All fans and pumps are fitted with Control Techniques Commander SK AC drives, each of which receives a speed reference from the controlling PLC system that monitors pressure, temperature (of cooled water), levels in the cooling water sumps etc and which also produces trend predictions.

The fans in the cooling tower are designated as main and standby, the drive for the standby only starting when the demand on the main fan drive exceeds 60 per cent.  On minimum speed, which is one fan at 40 per cent of full speed, the power demand is just 2.5 kW – described by Barklie as “the same as an electric kettle” – some 87.5 kW less than the old cooling tower. The average consumption per hour has now dropped from 242 kW to just 66 kW over all the pumps and fans associated with the water cooling system – a saving of 186 kW per hour – or over 4 MWh per day.

In addition to supplying cooling water for production requirements, the new cooling plant at Michelin’s Dundee plant also supplies chilled water to the air handling units to cool the factory in the summer months.  In the winter, the same system uses steam to provide space heating.